Pass collectionProperty through operators (Blender 2.8)
Thanks to batFINGER's comment, here is the working code: no need to pass arguments here, when calling operator : if it's stored in Scene, we can access to collection through context:

import bpy


# Assign a collection
class SceneSettingItem(bpy.types.PropertyGroup):
    name = bpy.props.StringProperty(name="Test Prop", default="Unknown")


class CallerOperator(bpy.types.Operator):
    """calls"""
    bl_idname = "object.caller_operator"
    bl_label = "Simple caller Operator"

    def execute(self, context):
        # Assume we have selected objects :
        selected = context.selected_objects

        # Create Collection :
        bpy.types.Scene.my_settings = bpy.props.CollectionProperty(type=SceneSettingItem)
        # clear collection:
        context.scene.my_settings.clear()
        # add in collection:
        for obj in selected:
            my_item = context.scene.my_settings.add()
            my_item.name = obj.name

        # call operator: 
        bpy.ops.object.called_op()
        return {'FINISHED'}


class CalledOp(bpy.types.Operator):
    """called"""
    bl_idname = "object.called_op"
    bl_label = "Called Operator"
    #selItems : bpy.props.CollectionProperty(type=SceneSettingItem)

    def execute(self, context):
        #read collection
        print ("collection = ",context.scene.my_settings)

        for obj in context.scene.my_settings:
            print(obj.name)

        return {'FINISHED'}


def register():
    bpy.utils.register_class(CallerOperator)
    bpy.utils.register_class(SceneSettingItem)
    bpy.utils.register_class(CalledOp)

def unregister():
    bpy.utils.unregister_class(CallerOperator)
    bpy.utils.unregister_class(SceneSettingItem)
    bpy.utils.unregister_class(CalledOp)


if __name__ == "__main__":
    register()

    # test call
    bpy.ops.object.caller_operator()